Hi all.
Recently joined the forum as particularly keen to thoroughly learn about SMPS's.
So, a friend asked if his 27" Samsung LED TV could be fixed.
The problem being that it would switch off after a few minutes and leave a black screen with a blinking red standby LED.
After finding one cap shorting out, all of the electrolytic caps were changed.
With the TV still laying screen down, it was switched on and left playing music and videos for some five hours or so, at which point it was decided to replace the back cover and test again.
What happened was that after reassembly, and back on it's 'feet', the TV then refused to switch on. Just a black screen with a standby LED which flashes twice, five times in a row.
And this is where we are still at.
The PSU is a BN44 00506A
No voltages on the PSU output with the boards connected.
If the cable between the power board and main board is disconnected, the backlights come on,
At that same time, the output voltages from the PSU read as follows.
Pins
1, 12.4v
2, 3.3v
3, 12.4
4, 2.3v
5, 12.4v
6, 4.7v
7, 12.4v
8, 0 v
9, 0 v
10, 0v
11, 5.2v
12, 5.2v
13,5.2v
14, 3.2v
Nothing appears burnt, nor have I found anything shorted.
The regulator chip is an STR W6053s.
I am wondering if something in the PSU is failing under load or whether the main board is shorting somewhere?
Any pointers will be greatly appreciated.
Recently joined the forum as particularly keen to thoroughly learn about SMPS's.
So, a friend asked if his 27" Samsung LED TV could be fixed.
The problem being that it would switch off after a few minutes and leave a black screen with a blinking red standby LED.
After finding one cap shorting out, all of the electrolytic caps were changed.
With the TV still laying screen down, it was switched on and left playing music and videos for some five hours or so, at which point it was decided to replace the back cover and test again.
What happened was that after reassembly, and back on it's 'feet', the TV then refused to switch on. Just a black screen with a standby LED which flashes twice, five times in a row.
And this is where we are still at.
The PSU is a BN44 00506A
No voltages on the PSU output with the boards connected.
If the cable between the power board and main board is disconnected, the backlights come on,
At that same time, the output voltages from the PSU read as follows.
Pins
1, 12.4v
2, 3.3v
3, 12.4
4, 2.3v
5, 12.4v
6, 4.7v
7, 12.4v
8, 0 v
9, 0 v
10, 0v
11, 5.2v
12, 5.2v
13,5.2v
14, 3.2v
Nothing appears burnt, nor have I found anything shorted.
The regulator chip is an STR W6053s.
I am wondering if something in the PSU is failing under load or whether the main board is shorting somewhere?
Any pointers will be greatly appreciated.
Attached Files
Comment